sYiiPHUS. 285 



quartus dorsalis, quintus nudus. Thoracis latera immaculata. Alee 

 areolis dlscaU et siibapicali margine posteriore fere eequaliter remotis et • 

 ilU parallelis, areola sudajjicnll intef/ra, loho axiUari distincto, venk 

 subcostali et radlali ad marcjinem disjunctis, vena transversa prcehra- 

 cJuali ante areolce discalis medium inse7'ia. Abdomen segmentis 5 {pel 

 6) tantum conspicuis. 



Head semicircular ; front even, convex ; epistoma hut little elongated 

 horizontally, a little compressed beneath the autenuaj, with some slight 

 tubercles above the peristoma, protuherant towards the mouth ; peristoma 

 oblong', straitened in front, directed upwards. Eyes bare or hairy. 

 Labrum curved, notched at the tip, much shorter than the labium. 

 Lingua pointed, nearly as long as the labium. Maxillai and pal])i of 

 vaiious length. Labium rather long, semicylindrical. Antenna) 5- 

 jointed, yom^(y shorter than the breadth of the head, seated a little above 

 the middle of the face, porrect, mitant, separated at the base ; first and 

 second joints small, bristly ; first clavate ; second short, transverse, 

 subeyathiform, oblique ; tliii-d large, oval ; fourth very small, seated on 

 the base of the third; fifth setiform, bare. Thorax oval, convex, hairy; 

 sides immaculate ; scutellum semicircular. Wings lanceolate, finely pu- 

 bescent, incumbent and parallel in repose ; discal and subapical areolets 

 nearly equidistant from and parallel to the posterior margin ; sicbapical 

 areolet entire ; axillary lobe distinct ; subcostal and radial veins ending 

 separately in the margin ; transverse praibrachial vein placed before the 

 middle of the discal areolet. Halteres uncovered. Abdomen depressed, 

 elliptical or linear, with only five {or six) segments apparent. Legs slender. 

 Male. Eyes contiguous. Fern. Eyes remote. 



The flight of the Syrphi is swift ; they often hover motionless 

 in the air, and then dart away. The larvte of many species feed 

 on Aphides ; they are oblong, depressed, narrow in front, broad 

 behind; the mouth is armed with a trident or three points, on 

 which they transfix their prey, and then raise it in the air, and 

 devour it. The larva of S.pyrastri feeds on the Aphis of the Eose; 

 it has six rows of tubercular feet, and seven feet in each row. 



"The dorsal vessel of the fly (e. g., S. pyrastri), instead of the 

 usual form which it had in the larva, assumes the shape of a flask, 

 having its long end directed towards the thorax ; the pulsation 

 and transmission of the fluid in it is manifest. This vessel 

 extends in length from the junction of the trunk with the abdo- 

 men to about the termination of the second segment. The in- 

 cluded fluid is propelled at intervals by drops, first from the wide 

 end towards the trunk, and then in the contrary direction. It is 

 conjectured that the neck of this vessel is composed of two or 

 more approximated tubes, and that the blood is conveyed forward 

 by the outward ones, and backward by the intermediate one ; also 



